For a helmet with a visor used as a safety cap at, e.g., a building site, a civil engineering construction site, or the like, to widen an upper visual field, a helmet with a transparent visor has been proposed (e.g., Japanese Patent Publication No. 298469: see Patent Document 1).
In the helmet 100 with a visor disclosed in the Patent Document 1, as shown in FIG. 11, a transparent visor 102 is integrally joined to a front bottom of a cap body 101. To increase strength of a joining portion of the cap body 101 and the visor 102, a plurality of engagement pieces 103 are formed in the joining portion of the visor 102, and a locking part 104 which is a notched part is formed between the engagement pieces 103. Further, thin outer edges 106 are formed in outer peripheries of both ends 105 of the visor 102.
For joining of the cap body 101 and the visor 102, first, the visor 102 is inserted to be set in an injection mold for injection-molding the cap body 101. Then, when the cap body 101 is injection-molded, the cap body 101 and the visor 102 are integrally joined to each other.
As described above, when the cap body 101 and the visor 102 are integrated, in the cap body 101, projections 107 are formed to sandwich both ends 105 of the visor 102 from upper and lower sides.
For the safety cap (helmet), for example, polycarbonate is used as a material because of its high mechanical strength and high heat resistance. Conventionally, the visor and the cap body have integrally been injection-molded. When the visor is configured to be transparent and the cap body is configured to be opaque, as described in the Patent Document 1, after the visor is preliminarily injection-molded, this visor is inserted to be set in the injection mold for injection-molding the cap body. Then, when the cap body is injection-molded, the visor and the cap body are integrally joined to each other.
In the injection molding, a fused resin is injected for molding in a cavity of the injection mold. In this case, when flowing front ends of the resin divided in the cavity merge with each other again, a resin temperature is lowered to inhibit complete integration. Thus, a thin weld line (weld mark) is formed. As can be understood from this, a temperature of the flowing front end of the resin in the cavity is low.
The visor of the helmet as the safety cap is thin, and the injection-molded cap body is also thin. Accordingly, even when the front end of the flowing resin during the injection-molding of the cap body comes into contact with a joining surface of the ends of the visor set as an insert in the mold, it is difficult to integrally and firmly joint the visor and the cap body to each other by sufficiently fusing the joining surface of the visor.
According to the Patent Document 1, the locking part of the notched shape is formed between the engagement pieces of the visor, and a locking hole is formed in the engagement piece. When the cap body is injection-molded, by setting a fitted state where the engagement piece of the visor is buried in the resin of the cap body or the resin of the cap body is intruded into the locking part/locking hole, the visor and the cap body are mechanically integrated.
Thus, the conventional configuration has problems as follows. That is, when there is a tendency that an external force is applied to the visor to concentrate stress in the joining portion of the visor and the cap body thereby causing deformation, the visor is easily peeled off from the cap body. As it is necessary in configuration to form the locking part, the locking hole or the like in the mold for injection-molding the visor, the configuration of the mold becomes complex.